Inter- and intraspecific female behavioral plasticity drive temporal niche segregation in two Tribolium species

Temporal niche segregation is a way to reduce competition over shared resources. Species with overlapping spatial niches often show plasticity and can use different activity times to minimize competition with and disturbance by other species. In many granivores, especially those living in their food resources, there is low competition over food, but other selective forces can drive distinct temporal activity times. Reproductive interference, that is, the interaction between individuals of different species during mate acquisition, can be such a driving force. Reproductive interference is a strong driving force for niche segregation between the co-occurring flour beetles Tribolium castaneum and Tribolium confusum (Coleoptera: Tenebrionidae). Nevertheless, most studies on Tribolium spp. evaluated other selective forces, such as resource competition, which are potentially weaker. Here, we aimed to characterize the species' peak activity time and its plasticity when exposed to a possible reproductive interference cue. We used a synthetic aggregative pheromone, shared by both species, as a cue for potential reproductive interference. We compared temporal niche plasticity between the sexes because reproductive interference is known mainly to reduce the female's fitness. We found that both species' activity times were hard-wired to an endogenous clock and that the sexes differed in their peak activity time and activity level. However, once exposed to the aggregation pheromone, only females shifted their activity time to match that of conspecific males, hence expressing more plasticity than the males to reduce Reproductive interference. These findings suggest an important role of the aggregation pheromone in the process of niche segregation.